A number of drugs which depress nerve function (e.g., halothane, diphenylhydantoin and phenobarbital) and some which are classified as anti-inflammatory agents (salicylates) have been shown to inhibit some lymphocyte functions and are suspected of possessing immunosuppressant activity. These drugs may be harmful to patients with marginal or embarrassed immune systems, (i.e., patients with cancer, patients recovering from certain viral infections, or cancer patients recovering from intensive chemotherapy or radiation treatment). In addition, one of the major functions of an intact immune system is to recognize and destroy foreign tissue including cells undergoing somatic or viral transformation leading to malignancy. Chronic treatment with weak immunosuppressant drugs may increase the incidence of cancer. The objective of this project is to study the effects of these drugs on a broad range of lymphocyte, granulocyte and monocyte (macrophage) functions related to various aspects of the immune response such as: 1. The mixed lymphocyte reaction in vitro; 2. The generation of cytotoxic lymphocytes in vitro and in vivo; 3. The mitogenic response of lymphocytes to phytohemagglutinin in vitro; 4. The response of bone marrow cells to colony stimulating factor in vitro; 5. The proliferation of bone marrow multipotential stem cells in vivo; 6. The survival time of mouse inoculated with transplantable tumor.